JPS61140933A - Method for controlling lamp for illumination of original - Google Patents

Abstract

PURPOSE:To minimize the light output at a low temp. by lighting up a lamp by the max. output of a lighting device for the specified time right after throwing of a power source and lighting thereafter the light by the prescribed low output. CONSTITUTION:The lamp 3 is lighted up by the max. output of the lighting device 2 only for the specified time right after throwing of the power source 1 and thereafter the output is changed over to the low output to the extent of maintaining the tube wall temp. of the lamp 3, by which the lamp is lighted up. The lamp electric power for maintaining said temp. is enough with <=1/3 the large output in general and this state is the standby state in which the lamp 3 is ready to be used anytime. The lighting device 1 is changed over to the prescribed output for copying which is preset and the lamp 3 is lighted up by the prescribed electric power when the copying operation is started. The lamp is again changed over to the electric power for maintaining the temp. and is put into the standby state when the copying operation ends. The lighting of the lamp 3 by the max. output to generate heat by itself is only for the specified time right after throwing of the power source and thereafter the low output for maintaining the temp. is simply required.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for controlling a document illumination lamp in a copying machine, a document reading device, etc.

BACKGROUND TECHNOLOGY In general, document illumination lamps are used in copying machines, etc.
If this is a light source with rapid temperature changes, such as a fluorescent light,
At low tube wall temperatures, particularly in the temperature range from 10° C. or lower to about 40° C., the light output changes drastically, exhibiting a change of 50% or more. In order to avoid this, it is sufficient that the tube wall temperature rises to nearly 40° C. at the time the lamp is used.

Therefore, in the past, a lamp was equipped with a heater, and the temperature was controlled by the heater to maintain the optimum temperature. However, according to this method, a heater and a temperature control device are required for the lamp, making the structure complicated and making lamp replacement inconvenient. Furthermore, since a heater is used, a safety device is also required to ensure the safety of this heater. Furthermore, with the heater method, there is a lot of thermal loss due to heat transfer between the heater and the glass, as well as heat conduction through the glass itself, and a large-capacity heater is required to uniformly heat the entire lamp in a short period of time. Become.

There are also devices that use the lamp's self-heating to keep the lamp lit even during standby. According to this, it is possible to avoid complicating the configuration, and to efficiently shorten the time (several 1
(0 seconds to 1 minute). However, the waiting time becomes longer.

This will increase the consumption of the lamp and shorten its lifespan.

Furthermore, some devices use a light output stabilizing device to compensate for changes in light output due to temperature changes.

However, in order to compensate for temperatures as low as 10° C., a large-capacity variable output lighting device is required, resulting in an increase in size.

This also adversely affects lamp life.

Purpose The present invention has been made in view of the above points, and can be achieved without using external heating means such as a heater.

An object of the present invention is to provide a document illumination lamp control method that can efficiently heat a lamp and minimize light output at low temperatures without adversely affecting lamp life.

Structure In order to achieve the above object, the present invention lights a lamp that is controlled by a lighting device to illuminate a document at the maximum output of the lighting device for a certain period of time immediately after power is turned on, and then lights it at a predetermined low output. It is characterized by allowing

Below, one embodiment of the present invention will be explained based on the drawings.0 This embodiment basically utilizes a self-heating method that can heat efficiently and in a short time. The lamp 3 is lit at the maximum output of the lighting bag W2 for only a certain period of time, and thereafter the output is switched to a level low enough to maintain the tube wall temperature of the lamp 3 and the lamp is lit. Here, it is generally sufficient that the lamp power for temperature maintenance is 173 or less of the maximum output. This state is a standby state in which the lamp 3 can be used at any time. When the copying operation starts, the lighting device 1 has a predetermined output for copying, and the lamp 3 lights up with a predetermined power. When the copying operation is completed, the lamp is switched on again to the power for maintaining the temperature, is turned on, and enters a standby state. In this embodiment, the lighting device 1 is a pulse width control type variable output lighting device that can adjust the output of the lamp. Therefore, the lamp output is set by the duty ratio of the pulse given as the lighting signal. Therefore, for example, when the duty ratio is 100%, the duty ratio for maximum output and temperature maintenance is 30%, and the duty ratio for copying is 50%.
Instead of such a stepless dimming method, a general step dimming method ballast may be used.

FIG. 1 is a timing chart showing the above-mentioned control operation. In FIG. 0, Pl is the maximum output, and P2 is the output necessary to maintain the tube wall temperature of the lamp 3.

P indicates the output for obtaining the amount of light necessary for copying.

Further, T indicates the time during which the lamp 3 is lit at maximum output.

By the way, it would be more effective if the time T0 during which the lamp 3 is turned on at maximum output and rapidly heats the tube wall is varied depending on the ambient temperature. That is, the ambient temperature inside the machine is detected when the power is turned on, and the time T can be determined according to the detected temperature value by referring to a table as shown below.

According to this table, for example, if the ambient temperature is 18°C when the power is turned on, the lamp 3 will be lit at maximum output for 15 seconds, and then the lamp 3 will be lit at a predetermined low output to maintain the tube wall temperature. Become.

With such a variable method, the time T for lighting at maximum output can be minimized. Such control can be easily realized by a CPU for controlling the copying machine.

Further, the above-mentioned time T0 is a period in which both the temperature change and the light amount change are severe. Therefore, if a copying operation is performed during this period, erroneous copies with significant density changes are likely to occur.Therefore, during the time T, copying operations are prohibited by means of prohibition or by displaying a prohibition display. Such control, which is preferably prevented from occurring, can be easily implemented within the control circuit. In other words, time T has elapsed since the power was turned on.

The warning display means may be turned on or copying may be prohibited during the period until the timer or counter that measures the timer or counter times up or counts up.

In this way, according to this embodiment, the lamp 3 lights up at maximum output and generates self-heating only for a certain period of time immediately after the power is turned on, and after that, a low output is required to maintain the temperature. Therefore, the lamp 3 can be efficiently heated with minimal adverse effects on the lamp life, and changes in light output due to low temperatures can be minimized. On this occasion,
Since no external heating means such as a heater is used, the configuration is simple.

Effects The present invention heats the lamp using the self-heating method as described above, but the lamp is lit at maximum output only for a certain period of time when the power is turned on, and thereafter the lamp is lit at a low predetermined output. The lamp can be heated efficiently without deteriorating the lamp life, and changes in light output at low temperatures can be minimized.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, with FIG. 1 being a timing chart and FIG. 2 being a block diagram.

Claims (1)

[Claims] A document illumination lamp control method characterized in that a lamp that is controlled by a lighting device to illuminate the document is lit at the maximum output of the lighting device for a certain period of time immediately after power is turned on, and thereafter is lit at a predetermined low output.